Various types of conveyors has been used for centuries to transport goods. Roller, belt, bucket, and screw conveyors each have their own advantages, and are widely used today in numerous applications. Various mechanisms have been used to power conveyors, and to alter the speed of the conveyors and thus the speed which goods are transported along the conveyor. Patents exemplary of devices to power a conveyor and/or to vary the speed of conveyors include U.S. Pat. Nos. 4,006,607 and 5,007,491.
Those familiar with conveyors and the transportation of goods appreciate that, like other types of conveyors, a linear motion conveyor has particular advantages. A linear motion conveyor, as defined herein, includes a generally elongate horizontal tray (or a tray slightly inclined from horizontal) having a supporting surface for the goods to be transported. In a typical application, the tray is moved slowly forward (slow forward speed) to convey the goods supported thereon, and is then pulled rearward at a fast rate (high return speed) so that the goods slide along the conveyor, thereby effectively transporting the products with respect to (along) the conveyor tray. Linear motion conveyors should not be confused with other types of conveyors, such as reciprocating conveyors or reciprocating screens, shuffle conveyors, vibrating conveyors, inertial conveyors, or shaker conveyors. Each of these other types of conveyors, as disclosed in U.S. Pat. Nos. 1,289,79 1, 2,027,284, 2,077,593, 2,079,360, 2,447,393, 3,212,630, 3,236,381, 3,253,700, 5,046,602, and 5,178,258, offers its own advantages and disadvantages when compared to linear motion conveyors. The drive of a linear motion conveyor thus generates repeated acceleration and deceleration of the tray or other supporting surface for the goods. While linear motion conveyors have been used to transport various types of goods, such conveyors are particularly well suited for transporting fragile goods, such as processed foods, which frequently become damaged when transported by other conveyors. Also, a linear motion conveyor may include a unitary support tray with optional integral supporting side surfaces, and accordingly cleanliness and sanitization are easily maintained for this type of conveyor.
Prior art drive mechanisms for conveyors are disclosed in the earlier referenced patents, as well as U.S. Pat. Nos. 1,293,556, 2,838,982, 3,486,608, 3,567,012, and 4,520,920. One type of prior art mechanism for driving a linear motion conveyor is adapted to be suspended from the elongate tray. Rotating fly wheels and attached members of the drive mechanism cause the tray to move slowly forward and quickly in reverse to produce the desired motion. This drive mechanism is, however, quite costly. Moreover, existing drive mechanisms for linear motion conveyors cannot be easily optimized by adjusting the ratio of slow forward speed to fast return speed to achieve the maximum product speed along a conveyor tray. The expense of the conventional drive mechanisms for linear motion conveyors and the high cost of maintaining such drive mechanisms have thus limited the acceptance of linear motion conveyors. By lowering the cost and improving the performance characteristics of the drive mechanism, new applications for using a linear motion conveyor will occur, and new industries will benefit from these and other features of a linear motion conveyor.
The disadvantages of the prior art are overcome by the present invention, and an improved drive mechanism for a linear motion conveyor hereinafter disclosed which overcomes the disadvantages of the prior art.